Fig. 5.

Effects of pretreatment with Ro 60-0175 (veh, 0.1–0.3 mg/kg) on second-order cocaine self-administration responding in squirrel monkeys (n = 3). Data (mean ± S.E.M.) are expressed as the percentage of responding maintained during ED_Max cocaine self-administration sessions after vehicle Ro 60-0175 pretreatment. Abscissa, unit dose of cocaine available for self-administration, relative to the maximally effective unit dose of cocaine (ED_Max) for each individual subject. Ordinate, normalized response rate.